H everyone! (all 52 followers!)
My last few month's efforts on Prototype 2 to build my own planetary/epicyclic gear train is almost at an end :(. But more later.
Firstly I videoed Prototype 1, let's call it PC1, in it's latest, almost working state:
You'll note the shadow of my fingers pushing it round as the roller doesn't have enough friction to drive the clock face disc. I have a potential solution to this courtesy of my brother the engineer: heat-shrink plastic sleeve:
Unfortunately the one sample sleeve he has fits perfectly around this larger roller (30mm) from PC2, but not the smaller 20mm roller from PC1, so i couldn't try it. Anyway given the noise and size of the motor with the built in gear down in PC1, i'm now moving onward and upward - so this idea stays on the back burner.
So what of PC2: building my own complex gear mechanisms...? More "learnings" here.
The main new idea in this design was to hide a gear chain inside the roller mechanism, which it achieves:
These print mostly nicely on my Prusa Mk2 (once it'd put a cardboard box around it to protect it from drafts):
Then the nasty engineering details enter the fray. The gears don't turn completely freely due to slight inconsistencies in the printing (visible by eye). Reducing the 'wall thickness' on the Cura slicer helped slighly. Also slowing down the head speed while printing (e.g. 80%).
But my little motor doesn't have enough torque to push past these so it always quickly jams. Last ditch attempt: helical gears which might avoid the jamming. Other suggestions welcome.
Otherwise i have prototype PC3 in planning: give up with cheap motors and switch to a Stepper motor: offering precise rotational control and high torque.
It's even bigger than the little motor, so the rollers are going to have to get bigger again - but that's just an opportunity to redesign the overall clock shape once again!